Safety catheters are widely used and typically include a catheter hub with a catheter tube extending distally thereof to be placed intravenously, a needle hub or support with a needle cannula extending distally thereof to a sharp distal tip and extending through the catheter tube to expose the sharp tip in order to facilitate intravenous insertion of the catheter tube, and a tip protector through which at least a portion of the needle shaft passes and adapted to enclose or otherwise shield the tip of the needle cannula after it has been withdrawn from the catheter tube and into the tip protector. The tip protector may also include a flexing feature which selectively engages the catheter hub to hold the tip protector to the catheter hub in a ready position with the sharp tip exposed and to readily come away from the catheter hub in a fired position with the sharp tip enclosed by the tip protector.
One type of design for the tip protector involves two axially shiftable components, one being an outer member which includes the catheter hub engagement feature and the other being an inner member which, in the ready position has the needle shaft passing therethrough, and in the fired position is closed down over the sharp tip. In that type of design, the inner member is positioned to block the catheter hub engagement feature in the ready position but when axially shifted into the fired position moves away from blocking the engagement feature of the outer member. In the ready position, the inner member limits the ability of the catheter hub engagement feature to flex radially inwardly and release engagement with the catheter hub such that the force required to remove the tip protector from the catheter hub is very high in the ready position. With such axially shiftable members, the needle cannula engages with the inner member as the sharp tip is pulled proximally toward and into the confines of the inner member to cause the inner member to slide axially relative to the outer member and into the fired position. In the fired position, the engagement feature of the outer member is no longer blocked by the inner member such that the engagement feature is able to flex (either due to its own bias or by interaction with the catheter hub) radially inwardly to come away from the catheter hub with relatively lower force, which is accomplished by further proximal movement of the needle cannula translating force from the inner member to the outer member to pull the tip protector proximally out of the catheter hub.